1. Field of the Invention
The present invention relates to a method for driving an ink jet head and an ink jet recording apparatus, which discharge ink according to an ink jet method to perform recording onto a recording medium, particularly relates to the method for driving an ink jet head and the ink jet recording apparatus, which utilize heat energy in order to discharge the ink.
In the invention, the term of “recording” shall mean not only to provide an image, such as characters and drawings, having a meaning to a recording medium, but also to provide the image, such as patterns, having no meaning to the recording medium.
2. Related Background Art
Recently, various kinds of recording apparatuses are used for a printer, a copying machine, a facsimile with a communication system, apparatus such as a word processor with a printer unit, and a recording apparatus combined with various processing apparatus. These recording apparatuses perform the recording to a recording medium such as paper, a string, fiber, cloth, metal, plastic, glass, wood, and ceramic. High-speed recording, high resolution, high image quality, low noise, and the like are demanded for the recording apparatuses. An ink jet recording apparatus can be cited as an example of the recording apparatus responding to such demands. In the ink jet recording apparatus, an ink jet head having a discharge port is used to eject an ink (recording solution) droplet, and the ink droplet adheres to the recording medium to perform the recording. Because the ink jet head is not in contact with the recording medium in the ink jet recording apparatus, extremely stable recording image can be obtained.
Among the conventional ink jet heads, the ink jet head which utilizes heat energy to discharge the ink can array many discharge ports in high density. Therefore, the ink jet head which utilizes heat energy to discharge the ink has advantages that high-resolution recording can be performed and the downsizing can easily be achieved.
In the conventional ink jet head which utilizes the heat energy, generally the high density is achieved by arraying a plurality of heat generating members in line on a base body such as silicon, and a common heat accumulation layer and a common electrical insulation film are formed for the plurality of heat generating members (see Japanese Patent Application Laid-Open No. 2001-171127 and Japanese Patent Application Laid-Open No. 2002-11886).
FIG. 15 is a schematic sectional view showing a heat generating member (heater) of the conventional ink jet head which utilizes the heat energy.
As shown in FIG. 15, an ink jet head 100 has a base body 120 in which a heat generating member 123 is formed and a nozzle material 110 which is connected onto the base body 120. The base body 120 has a heat accumulation layer 122 in which a plurality of layers such as a thermal oxide film are formed on a surface of a silicon substrate, the heat generating member 123 which is partially formed on the heat accumulation layer 122, electrode wirings 124 and 125 which supplied electric power to the heat generating member 123, an electrical insulation film 126 which is formed so that the heat generating member 123 and the heat accumulation layer 122 are covered with the electrical insulation film 126, and a cavitation-resistant film 127 which is formed on the electrical insulation film 126 and made of Ta. Both the electrical insulation film 126 and the cavitation-resistant film 127 constitute a protection film 128. The nozzle material 110 is bonded to the base body 120 to form a liquid path including an ink chamber 112 located above the heat generating member 123. In the nozzle material 110, a discharge port 111 is formed at an opposite position to the heat generating member 123.
The ink chamber 112 is filled with the ink, and the heat generating member 123 is heated by applying voltage to the heat generating member 123 through the electrode wirings 124 and 125. The ink in the ink chamber 112 is abruptly heated to generate film boiling by heat generation of the heat generating member 123. Therefore, a bubble is generated in the ink, and the ink is discharged from the discharge port 111 by pressure based on growth of the bubble.
In order to efficiently transfer the heat energy generated by the heat generating member 123 to the ink, various ideas for a film structure of the base body 120 have been proposed.
Referring to FIG. 16, a principle of heat transfer by the heat generation of the heat generating member 123 will be described. In FIG. 16, heat quantity Q is applied to the heat generating member 123 by energizing the heat generating member 123. The heat quantity Q is vertically dispersed to become heat quantities Q1 and Q2. The heat quantity Q1 dispersed upward is transferred to ink 130 on the protection film 128 formed by the electrical insulation film and the cavitation-resistant film. This allows a bubble 131 to be generated in the ink 130 to perform the discharge as described above.